Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$60.74	3.559%	$62.9017	$62.90	$62.90	$62.90
Purchase #2	$78.53	13.179%	$88.8795	$88.88	$88.90	$88.90
Purchase #3	$108.35	5.468%	$114.2746	$114.27	$114.25	$114.30
Purchase #4	$139.73	11.477%	$155.7668	$155.77	$155.75	$155.80
Purchase #5	$234.99	3.636%	$243.5342	$243.53	$243.55	$243.50
Purchase #6	$43.44	6.614%	$46.3131	$46.31	$46.30	$46.30
Purchase #7	$140.65	13.208%	$159.2271	$159.23	$159.25	$159.20
7 purchase totals =	$806.43		$870.8970	$870.89	$870.90	$870.90